Conventionally, rotating electrical machines include a stator fixed to the inner circumferential surface of a motor housing, and a rotor rotatably attached to the motor housing so as to face the stator in the radial direction (see, for example, JP 2013-207968A). Such a conventional electrical rotating machine may function as an electrical motor in which external electric power is supplied to rotate the rotor, or function as a generator in which the stator generates electric power due to the rotor rotating.